1. Field of the Invention
This invention relates to an improved car plug used to derive power by utilizing a socket, that is, a jack portion for a cigar lighter, mounted in a cabin of an automobile, for a socket to derive power, i.e., by inserting the plug, instead of the cigar lighter, into the socket after removal of the cigar lighter from the socket.
2. Description of the Prior Art
A cigar lighter socket 1 mounted in a cabin of an automobile has a cylindrical main body 10 serving as an external electrode and formed by a metal material and is assembled as shown in FIG. 1. In this case, an axial rod-shaped internal electrode 11 is mounted as one body to the bottom of the main body through an insulating material 12. Further, a holding piece 13 formed in the shape of a plate by an elastic metal material for holding the cigar lighter inserted into the main body 10 is mounted to the inner end side of the internal electrode 11. Further, a cord holder 15 is mounted to the outer end side of the internal electrode 11 projecting from the outer surface of the bottom of the main body 10 through an insulating material 14 with a nut 16 to hold an earth wire electrically connected to the main body 10 and a cord 17 electrically connected to the internal electrode 11 in the cord holder, resulting in a completion of assemblage of the socket which is then mounted in a vehicle body.
A car plug A inserted into the socket to derive power has a body 2 formed in an axially cylindrical shape by an insulating material and is assembled as shown in FIG. 2. In this case, an internal electrode terminal 3 formed by a conductive metal material is mounted to the tip end (i.e., the left end side in FIG. 2) of the body as being moved freely inwardly and outwardly. Further, one cord wire 40 of a cord 4 inserted into the body 2 from its tail end side (i.e., the right end side in FIG. 2) is connected to the internal electrode terminal through a fuse 30 in the state that the internal electrode terminal is urged to be pushed out by a spring 31. Then, external electrode terminals 5, 5 formed by an elastically conductive metal band plate are incorporated into the body 2 such that protuberant portions 50, 50 at the tip end side of the external electrode terminals are extended from the circumference of the body 2 through window holes 20, 20 provided in a peripheral wall of the body 2, and the tail ends of the external electrode terminals are connected to the other cord wire 41 of the cord 4 by soldering, resulting in a completion of assemblage of the car plug. When the car plug is inserted into the above socket 1 shown in FIG. 1, the internal electrode terminal 3 at the tip end of the car plug is brought into electrical contact with the internal electrode 11 at the bottom of the cylindrical main body 10 of the socket 1, and the protuberant portions 50, 50 extending from the circumference of the body 2 are also brought into electrical contact with the inner surface of the cylindrical main body 10 of the socket 1. For that reason, the car plug is used to derive power through the cord 4.
Incidentally, the cigar lighter socket 1 mounted in a vehicle body of Japanese and U.S. automobiles is standardized to have the main body 10 having an inside diameter of 21 mm. On the other hand, a socket 1' used for European automobiles such as Benz is formed to have the main body having a somewhat larger inside diameter (about 22 mm), as shown in FIG. 3.
For that reason, in case of attempting to derive power by inserting the car plug A formed to be adapted for the Japanese automobiles to derive power into the socket 1' for the European automobiles, the protuberant portions 50, 50 of the car plug A are brought into insufficient contact with the inner surface of the main body 10 of the socket 1'. As a result, there are problems such as a drop of the car plug A out of the socket or a failure in electrical connection between the protuberant portions 50, 50 and the main body 10.
In this connection, the car plug A has a support member s in the body 2 to support the external electrode terminal 5 such that the protuberant portion 50 may be extended from the window hole 20 of the body 2. The support member is also axially supported with a rotary shaft r rotated by operations from the outside of the body 2 to shift a supporting position in the radial direction of the body by the pivotal motion of the support member, as shown in FIG. 4. Thus, the car plug is structured to cope with variations in inside diameter of the main body 10 of the socket 1 by switch-over of the supporting position such that the extension level of the protuberant portion 50 from the window hole 20 may be switched over between higher and lower levels.
When the above car plug A in the prior art is inserted into the somewhat larger socket 1' for the European automobiles, the extension level of the protuberant portion 50 is switched over to the higher level by operating an operating portion to move the support member s to a position in the state shown in FIG. 4 so as to support the longitudinal portion of the external electrode terminal 5 as being pushed out in the radial direction. When the car plug A is inserted into the somewhat smaller socket 1 for the Japanese and U.S. automobiles, the extension level of the protuberant portion 50 is switched over to the lower level by operating the operating portion similarly to place the support member s in the state shown in FIGS. 2 and 6 so as to separate the support member s from the external electrode terminal 5. Thus, the above car plug A is adapted for both the somewhat smaller socket 1 and the somewhat larger socket 1' by switch-over operation. However, since the above switch-over operation is complicated, and the support member s mounted in the body 2 to be out of sight needs to be moved from the outside of the body 2 for the switch-over operation, it is difficult to make sure of the switched-over state. Thus, a mistake in inserting the car plug set to be adapted for the somewhat larger socket 1' into the somewhat smaller socket 1 is made in some cases. In this case, there is a problem in that the forcible insertion of the car plug causes a breakage of the car plug or makes a removal of the car plug from the socket impossible.